netd: bandwidthcontroler: add support for alerts via iptables' quota2 log messages

* Fix quota2 updating. The old insert-new/delete-old scheme doesn't work as the kernel
 keeps the old counter assigned to the new rule.

* Add support for setting dummy quotas used only for alerts.

This needs:
 - new kernel with quota2 changes that support logging via NETLINK's
   NETLINK_NFLOG family.
 - NetlinkManager support for receiving the events.
 - java land handler for these new events.

* new commands
  - add/remove a dummy quota to generate an alert after <bytes> are seen including loopback.
    alerts are only triggered once.
    . ndc bandwidth setglobalalert <bytes>
       calling it multiple times, just re-arms the alert for the specified number of bytes.
        Use "ndc bandwidth getiquota singleAlert" to get what is left.
    . ndc bandwidth removeglobalalert
  - add/remove alert on a shared quota (similar accounting as shared quota)
    . ndc bandwidth setsharedalert <bytes>
        Requires that a shared quota already exist.
    . ndc bandwidth removesharedalert
        Removing the last of the shared quotas will remove the matching alert.
  - add/remove alert on an interface (similar accounting as interface quota)
    . ndc bandwidth setinterfacealert <iface> <bytes>
        Requires that a interface quota already exist.
    . ndc bandwidth removeinterfacealert <iface>
        Removing the interface quota will remove the matching alert.
  - get the quotas and alert leftovers
   . ndc bandwidth getquota
      shared quota leftover
   . ndc bandwidth getiquota <quota_name_or_iface>
      iface specific quota leftover
      Can be used to read-out alerts. E.g.
        setglobalalert 12345 -> getiquota globalAlert
        setsharedalert 12345 -> getiquota sharedAlert
        setinterfacealert iface0 12345 -> getiquota iface0Alert

Change-Id: Iea9698b9d20e713281755dac32b4772a6cf0e84e